Sensors are being manufactured in ever decreasing sizes. For example, credit cards are issued with radio frequency identifier (RFID) tags embedded thereon that are energized when subjected to radio frequencies of certain wavelengths. In an exemplary application, a radio wave emitter that is external to the card can be configured to output radio waves at a certain frequency, which is configured to energize the RFID tag. Responsive to the RFID tag being energized, such tag can emit data by way of an antenna at a frequency that is monitored by an RFID reader. Such data can be indicative of the identity of the owner of the credit card, the account number of the credit card, an expiration date of the credit card, or the like. When the RFID tag ceases to receive energizing radio waves from the radio wave emitter, the RFID tag ceases to emit data.
In another example, an RFID tag can include a power source. In such a configuration, the RFID tag is configured to continuously (or periodically) output a signal until a charge of the battery is dissipated. In most commercial applications, the RFID tags do not include a power source, due to size constraints and costs corresponding to batteries.
In either configuration, RFID tags can be relatively small in size. Reduction in size of RFID tags, however, is limited, as RFID tags include an antenna to output data by way of radio waves. Furthermore, RFID tags are generally not autonomous, as typically RFID tags must be activated by an external energy source to output data.